When we think of electronic communications it is natural to think first of television because we see it so frequently. While television is an extremely important part of the communication area, we should not limit our thinking to it alone. If we take electronic communications to mean the conveying of information from point-to-point by means of electromagnetic waves, then we must consider many applications other than television. Radiotelephony and radiotelegraphy are perhaps the most obvious of these other applications. Less obvious, but nevertheless extremely important, are the various types of radar, telemetry, and remote control applications.

Each of these many application areas is a technical specialty within itself. We could never hope to cover all of them in detail within a single volume. There are, however, a number of basic communication principles which are shared by all of these application areas. In this volume we shall cover a number of these basic areas including: receivers, transmitters, and introductory communications systems. Try to keep in mind that while a principle may be illustrated by a specific application, the principle applies to many other applications as well.